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The Department of Energy (DOE) Pantex Plant near Amarillo, Texas, does not pose a threat to public health from anysite release at this time based on currently available environmental sampling data. No site-related contaminants arecurrently accessible on- or off-site at levels that would cause adverse health effects. On-site variations have appearedin specific areas of the Pantex Plant; however, monitoring and surveillance off-site did not exceed normal variations. The on-site areas where variations appeared were associated with the burning grounds and the radioactive solid wastemanagement unit. The DOE continues clean-up activities at the Pantex Plant with oversight provided by the TexasNatural Resources Conservation Commission and the Texas Department of Health (TDH).

In evaluating residents' public health concerns, the Agency for Toxic Substances and Disease Registry (ATSDR)obtained the assistance of the TDH Bureau of Epidemiology. A synopsis of the evaluation of residents' concernsfollows. Residents raised questions about excessive cancer rates in Carson, Potter, Randall, and Armstrong counties,excessive birth defects, and other adverse health effects they believed to be related to environmental releases from thesite. Although the number of cases and/or deaths reported for some types of cancers in those counties may be higherthan what would be expected based on comparison with numbers for other populations, an ATSDR review ofavailable environmental data indicated that it is unlikely that area residents come into contact with significant enoughamounts of chemicals or radioactive substances from the plant to cause adverse health effects. Thus, the Pantex Plantis probably not the cause of the higher than expected levels of cancer found in this area. The concern that theoccurrence of birth defects was elevated in the counties surrounding Pantex required the evaluation of informationobtained from birth certificates, fetal death certificates, and infant death certificates. The number of children born inthis area with certain categories of birth defects appears to be higher than what would be expected based on similarbirth defect information obtained for the entire State. To determine an underlying cause for the apparent increase,TDH evaluated parental occupation and place of employment as well as distribution of the birth defects by zip code. No occupations or workplaces for mothers or fathers were notable. Very few parents of children reported to have beenborn with birth defects worked at the Pantex facility. Additionally, although one zip code near the plant (79107,which extends from the western edge of the Pantex Plant along the Potter County/Carson County border towardsAmarillo) showed significant elevations for several birth defect categories, there was no consistent pattern among zipcodes showing that closer proximity to Pantex increased the risk of birth defects.

An investigation of the incidence of low birthweight babies concluded that although there was an increase inArmstrong County, there was no pattern that would suggest that proximity to the Pantex Plant increased the risk ofhaving a low birthweight baby. An evaluation of the number of people with muscular dystrophy, multiple sclerosis,amyotrophic lateral sclerosis, and lupus erythematosus in the area indicated a higher than expected number of deathsfrom all but lupus erythematosus. There was no consistent pattern of deaths from these diseases in the four-countyarea. In some instances, the number of deaths due to these diseases was elevated for males and not females; in other instances, the reverse was true. The causes of many of these diseases are notclearly understood. Detailed answers to questions about patterns of disease occurrence follow.

1. Is there a higher than expected number of birth defects in this area?

Possibly. Using information obtained from birth certificates, fetal death certificates, and infant death certificates, theTexas Department of Health Birth Defects Monitoring Division (TBDMD) found that the observed cases and/ordeaths reported for several categories of birth defects in this area are higher than what would be expected based oncomparison to State rates. Specifically, the TBDMD looked at birth defect information for Armstrong, Carson, Potter,and Randall counties for the years 1990 to 1994 and found the following:

birth certificate information showed that several categories of birth defects were significantly elevated in specificcounties and in the four counties grouped together, fetal death certificate information showed a statisticallysignificant excess of hydrocephalus in Carson County anda statistically significant excess of "other congenitalanomalies" in Potter County, and infant death certificate information showed a statistically significant excess in two major heart defects in CarsonCounty.

Should the public be worried about these results, and what do they mean?

The public should not be worried. In some instances, even though the results are statistically significant, they arebased on few observed cases and wide confidence intervals. Thus, we would not interpret these results as indicatingan increased risk for birth defects. In other instances, the birth defect categories were nonspecific. Because thesecategories include many different types of defects, it is impossible to determine whether the increase is the result ofslight (nonsignificant) elevations among several types of defects or the result of a large increase in one or two defects.

For Potter County, Randall County, Potter and Randall counties combined, and the combined four-county area,several of the clinically specific birth defect categories appeared elevated. Although we are fairly certain that thesestatistical findings are real and not solely due to chance, there are other possible explanations for these results.

One possible explanation for the higher than expected number of reported birth defects in this area is that compared tothose in other areas of the State, local health care providers may be more careful to report birth defects on the birthcertificates. When a child is born with a birth defect, attending health care providers or hospital personnel mayindicate the presence of a birth defect by checking off 1 of 23 categories of birth defects listed on the birth certificate. In an attempt to rule out better reporting as a possible explanation for the apparently higher number of reported birthdefects, the TBDMD compared the reports of birth defects from this area to what would be expected based on theexperience of two active surveillance systems (California and Atlanta). Active surveillance systems are best atcapturing the true occurrence of disease in populations. In these systems, public health workers visit hospitals andother health care facilities to review and record pertinent information from medical records. Using information fromthese systems for comparison, no statistically significant excesses in reported birth defects were found in the fourcounties. Thus, we cannot rule out better reporting as a possible explanation for the apparently higher than expectednumber of birth defects reported for this area. However, we cannot rule out the possibility that the apparent excess isreal.

2. Could the Pantex Plant be the cause of the higher number of birth defects observed?

Not likely. ATSDR review of available environmental data indicates that it is unlikely that residents are coming intocontact with significant amounts of chemicals or radioactive substances from the Pantex Plant. Thus, it is not likelythat the Pantex Plant is associated with these results. Currently, the causes of two-thirds of birth defects remainunknown. Many birth defects have a multifactoral etiology, meaning that a variety of both genetic and environmental(diet, lifestyle, and occupational) factors play a role. For example, microcephaly may be caused by one of severalinherited syndromes or by degenerative brain disorder, birth trauma, intrauterine infection, or exposure to X rays inutero. The causes of tracheo-esophageal fistula, cleft lip, cleft palate, and club foot are thought to be multifactoral. Esophageal atresia is thought to arise from a random, generalized insult to embryogenesis. Most cases of polydactylyor syndactyly have a genetic cause. The wide range of birth defects for which statistically significant excesses werenoted argues against a single causative physical or chemical agent.

In an attempt to better answer this question, TBDMD did a subsequent analysis of the birth defect informationobtained from the birth certificates. Specifically, staff looked at parental occupation and place of employment as wellas the distribution of the birth defects by zip code. There were no occupations or workplaces that seemed unusual formothers or fathers. Several fathers of children with birth defects worked in meat processing, but this is common inAmarillo. Very few parents of children reported to have been born with birth defects worked at the Pantex Plant. Additionally, although one zip code near the plant (79107) had significant elevations for several birth defectcategories, other zip code areas also had significant elevations; there was no consistent pattern showing that closerproximity to Pantex increased the risk of birth defects. Fastidious reporting practices by the hospital that delivers themajority of live births in this area could explain these results.

3. Is there a higher than expected number of low birthweight babies born in this area?

Yes, in Carson and Potter counties. Information obtained from birth certificates (1990-1994) indicates the rate of lowbirthweight babies born in Carson and Potter counties was higher than the rate reported for the State of Texas. However, the rate of low birthweight babies born in the other two counties (Randall and Armstrong counties) was notsignificantly different from the rate for Texas.

Should the public be worried about these results?

The public should not be worried. The higher than usual rate of low birthweight babies born in Carson and Pottercounties could in part be the result of the reporting practices of the hospital that delivers the majority of babies in thisarea. Northwest Texas Hospital strictly adheres to the policy of the Texas Department of Health to file a birthcertificate for all live births regardless of gestational age, and previous discussions with hospital staff indicate that allinfants with any life signs, regardless of gestational age, are considered live births. The practice of reporting verypremature births as live births may not be uniform throughout the State. Some hospitals may report very prematurebirths as fetal deaths, and some may not report premature births with gestational ages less than 20 weeks.

4. Could the Pantex Plant be the cause of the higher rate of low birthweight babies?

Not likely. Although reporting practices may not completely explain the elevated rates for this area, there are severalrisk factors that increase a woman's chances of giving birth to a baby born with a low birthweight. Mothers whosmoke, drink alcohol, use illicit drugs, or have poor nutritional habits during pregnancy may have an increased risk forlow birthweight babies. In addition, maternal age and the number of previous live births are other examples of factorsthat can have an effect on the developing fetus. In summary, there are many factors, some of which can be controlledby the mother and others that cannot, that play an important role in the health of the developing fetus.

There was no pattern observed that would suggest that proximity to the Pantex Plant increased the risk of having a lowbirthweight baby. Additionally, an ATSDR review of available environmental data indicates that it is unlikely thatresidents are coming into contact with significant amounts of chemicals or radioactive substances from the PantexPlant. Thus, it is not likely that the Pantex Plant is associated with these results.

5. Is there a higher than normal amount of cancer in this area of the State?

Yes, for some types of cancer. The number of cases and/or deaths reported for some types of cancers in this area maybe higher than what would be expected based on comparison with other populations. The Texas Department of HealthTexas Cancer Registry (TCR) looked at cancer records for Armstrong, Carson, Potter, and Randall counties and foundstatistically significant excesses for some types of cancer. Specifically, the TCR looked at records for lung, bone,prostate, breast, brain, and thyroid cancer, leukemia, and all types of cancer combined and found the following:

a higher than expected number of females who have cancer (all types combined) in the combined Potter/Randallcounties area;

a higher than expected number of males who have chronic lymphocytic leukemia in the combined Potter/Randallcounties area;

a higher than expected number of males who died from prostate cancer in Potter and Randall counties; and

a higher than expected number of males who died from cancer (all types combined) in Potter County.

Should the public be worried about these findings, and what do they mean?

The public should not be worried. The higher than expected number of females with cancer (all types combined) inthe combined Potter/Randall counties area and the higher than expected number of males who died from cancer (alltypes combined) in Potter County are difficult to evaluate with any degree of certainty. The excesses are small andthe categories are nonspecific and include all types of cancer. The results could be the result of slight (nonsignificant)elevations among many different types of cancer or the result of moderate (nonsignificant) increases in one or twocancer site locations.

The higher than expected number of males with chronic lymphocytic leukemia (CLL) in the combined Potter/Randallcounties area may be noteworthy. In a previous investigation, the TCR found a slight excess of CLL among femalesfrom this area. The causes of CLL are not known, and although there is some evidence that there may be an inheritedsusceptibility component to this disease, it is our opinion that the significant excess of CLL deserves furtherinvestigation.

The higher than expected number of males from Potter and Randall counties who died from prostate cancer also isnoteworthy and deserves further attention. The fact that a higher number of males who have prostate cancer was notfound suggests that late detection and treatment of this disease may be contributing to the higher number of deathsfrom this disease. Increased awareness and attempts to improve the early periodic screening for this disease in thisarea may be needed.

6. Could the Pantex Plant be the cause of the higher than expected number of people withcancer that the TCR observed?

Not likely. Cancer is a very common disease, much more common than most people realize. Approximately four outof every ten persons alive today will develop some type of cancer in their lifetime. Furthermore, cancer is not onedisease, but many different diseases. Different types of cancer are generally thought to have different causes. InTexas, as in the United States, cancer is the second leading cause of death, exceeded only by heart disease. In 1995,Texas reported 31,571 cancer deaths. Sixty-five percent of these deaths were of persons 65 years of age or older. Finally, it takes time for cancer to develop, usually 20 to 40 years. The occurrence of cancer may vary byrace/ethnicity, gender, the type of cancer, geographic distribution, population under study, and a variety of otherfactors. Scientific studies have identified a number of factors for various cancers that may increase an individual's riskof developing a specific type of cancer. These factors are known as risk factors and include the following: heredity,diet, age (cancer risk increases with age), family history, exposure to certain chemicals (only a limited number ofchemicals show definite evidence of human carcinogenicity, e.g., benzene, asbestos, vinyl chloride, arsenic, aflatoxin),radiation (ionizing radiation and ultraviolet radiation), alcohol, and tobacco smoke.

The chances of a person developing cancer as a result of exposure to an environmental contaminant are actually slight. Tobacco use and diet are estimated to cause 30% and 35% of all cancer deaths respectively or 65% total for all cancerdeaths. Pollution and occupational exposures collectively are estimated to cause 4-6% of all cancer deaths.

A careful review of available environmental data by ATSDR indicates that it is unlikely that area residents are cominginto contact with significant amounts of chemicals or radioactive substances from the Pantex Plant. Thus, the PantexPlant is probably not the cause of the higher than expected levels of cancer found in this area.

7. Is there a higher than usual number of people with muscular dystrophy, multiplesclerosis, amyotrophic lateral sclerosis, and lupus erythematosus in this area?

Possibly. Because these diseases are not reportable in Texas, the Texas Department of Health (TDH) was not able todetermine the number of people who have these diseases; however, to try to answer this question, the TDH revieweddeath certificates from this area to determine how many people died from each of the diseases. The TDH did find ahigher than expected number of deaths from some of these diseases for this time period. In Carson and Pottercounties, a higher than expected number of males died from muscular dystrophy. In Randall County, a higher thanexpected number of females died from multiple sclerosis. In Potter and Randall counties combined there was a higherthan expected number of females who died from multiple sclerosis and a higher than expected number of males diedfrom amyotrophic lateral sclerosis. Deaths due to lupus erythematosus were not found to be higher in any of the four counties investigated.

Should the public be worried about these results?

Probably not. Incidence data were not available for these diseases; therefore, we used mortality data. For severalreasons, mortality data may not be a good indicator of the actual occurrence of these diseases in the population. Individuals may live for many years with these and other chronic diseases, and death may ultimately result from othercauses. Caution must be exercised when interpreting the elevations in the four-county area. All of the counties aresparsely populated, and even one additional death can result in an elevated mortality ratio.

Because of the nature of these data, we are not able to provide, with any degree of certainty, a meaningfulinterpretation. The causes associated with each of these diseases are still very speculative.

For muscular dystrophy, genetics is a major risk factor. This means that individuals who have relatives with thedisease may have a greater chance of developing the disease themselves.

Multiple sclerosis, like muscular dystrophy, also may have a genetic component associated with its development. Inaddition, other factors that potentially have been associated with this disease include exposure to viral agents, countryof origin, exposure to heavy metals, and being female.

Several possible risk factors that may be associated with amyotrophic lateral sclerosis (ALS) have been discussed inthe scientific and medical literature. Genetics, prior trauma, heavy milk consumption, heavy physical labor,occupational exposure to chemicals involved in the manufacture of plastics, and exposure to infectious agents beforethe onset of disease all have been implicated in the development of ALS.

Lupus erythematosus also has a strong genetic association with its development. In addition, exposure to specificchemicals and toxins, dietary factors, and exposure to infectious agents before the onset of disease have beenassociated with lupus.

8. Could the Pantex Plant be the cause of the higher than usual number of deaths frommuscular dystrophy, multiple sclerosis, and amyotrophic lateral sclerosis, observed in this area?

Not likely. There was no consistent pattern of deaths due to these diseases found in the four- county area. In someinstances, the number of deaths due to these diseases was elevated for males and not females; in other instances, thereverse was true. The causes of many of these diseases are not clearly understood. Additionally, ATSDR did not findany evidence that area residents are coming into contact with significant amounts of chemicals or radioactive substances from the Pantex Plant.

9. What are the potential health effects of gaseous tritium releases (the last one recorded in 1989)?

In 1982, more tritium was released to the atmosphere than in previous years. In 1982, the maximum levels of tritium in air ranged from 0.059 - 0.24 Bq/m3 (1.6 - 6.4 pCi/m3). Although there was more tritium released than usual, theestimated doses were less than the radiation exposure from the normal background (natural radiation sources). In1985, elevated levels of tritium were detected off site; however, the levels were still below levels that would causeadverse health effects and, for comparison, below levels of NRC compliance.

A major release of tritium from the assembly area occurred in 1989. Dose assessments developed by the Departmentof Energy (DOE) and reevaluated by Battelle in 1994 suggested that tritium doses were well below levels known tocause adverse health effects. As late as 1994, continuously decreasing doses of tritium continued to be released fromthe dome and surrounding soil. The Battelle reassessment of the tritium release model used indicates that doses from1990 to 1992 ranged from 4 to 70 x 10-6 mrem. The greatest contributors to those doses were fruits and nonleafyvegetables. Air monitoring for radionuclides (uranium [U], plutonium [Pu], and tritium) in the 1990s shows theatmospheric concentrations of the U and Pu radionuclides to be at levels that would not cause adverse health effects. Comparisons of air concentrations around Pantex with those for Austin and El Paso, Texas, show the air aroundPantex actually contains less radiological contaminants than the air in those two cities.

Tritium concentrations have been elevated around Pantex in the past as a result of a major release in May 1989. Theelevated tritium levels, however, have not resulted in radiation exposures or doses above levels that would causeadverse health effects.

Although chemical contamination above screening values has been detected in the perched aquifer at the southeasternplant boundary, that particular perched aquifer is not used as a water source downgradient of the contaminant plume. If used as a water source in the future, water from that perched aquifer would require treatment to removecontamination before it would be safe for consumption. Chemical contamination above screening values has not beendetected in the Ogallala aquifer, which is used as a drinking water source throughout the region. Samples from thePantex Plant production wells are used as a secondary check for possible chemical migration from the perched aquiferinto the Ogallala aquifer. If contamination of the Ogallala aquifer were to occur as a result of Pantex Plant operations,it would appear first in the production wells. The Pantex Plant production wells, therefore, serve as interceptor wellsfor the downgradient City of Amarillo drinking water production wells. The Pantex Plant and City of Amarilloproduction wells are also monitored in accordance with Safe Drinking Water Act requirements for source water. Monthly sampling of an additional off-site water quality monitoring station, the water supply at Bushland, Texas,provide control data for comparison with data from the plant. This control well is completed in the Ogallala aquiferupgradient from Pantex Plant and is not affected by plant operations.

11. What is the potential for airborne exposure as a result of open burning anddispersal of explosive residues and sediments from Pantex dry surfaceimpoundments?

The Pantex Plant has a state-issued permit that provides limits on burning at the burning ground. Before the permit was issued, an air dispersion model calculated that the permit limits would protect public health andthe environment. In addition, the permit requires monitoring of air, soils, vegetation, surface water, and groundwater. This monitoring has shown that burning has not resulted in releases outside the burning ground.

The entire burning ground was identified as multiple solid waste management units (SWMUs). The environmentalinvestigations concentrated on the old solvent evaporation pit and the landfills. In addition, surface soil samples weretaken around the burn pads and the burning ground complex. The sample results showed higher than backgroundlevels for explosives, and those areas with the highest levels are scheduled for cleanup in calendar year 1998. Becausethe area is covered with grass, movement of the explosives will occur only if the land is disturbed.

The 11-14 SWMU pond liner and sediments were removed and replaced with clean soil in the former impoundment. The surface impoundment at SWMU FS-16 was also removed and filled with clean soil.

Environmental investigation fieldwork was completed in 1995 for playas 1, 2, 3, and 4 and Pantex Lake. Surface andsubsurface soils were sampled, and the results for all substances except arsenic and beryllium were withinenvironmental guidelines; however, the amounts of these two materials were at or below background levels in soilsnormally found in similar playas in the geographic area.

12. Can asbestos from the asbestos disposal area in the northeastern corner of theplant blow off site?

Landfills 1 and 2 are in the northeastern corner of the plant. Although asbestos was put in Landfill 1, vegetationcovering the area prevents release to the air. Landfill 2 has no confirmed asbestos material based on results of theRCRA Facility Investigation. The Landfill 1 maintenance cover, which consists of a 2-foot thick, compacted soilcover, a 6-inch thick topsoil layer and vegetation, has not been disturbed or plowed and is not grazed. It wasoriginally seeded with a mixture of hard red winter wheat, Blue Gramma, and Sideoats Gramma.

13. What is the public health impact of previous discharge of waste waters fromPantex and the old Air Force base to Pantex Lake, an off-site, naturally occurringplaya northeast of the plant?

Pantex Lake received discharges from the Old Sewage Treatment Plant via an underground pipeline from 1942 untillate 1970 or early 1971. An environmental investigation of the treatment plant, which included the sludge dryingbeds, recommended no further action.

Environmental samples were collected beginning around 1970. The 1995 results showed the water at Pantex Lake tobe similar to that in the other playas. Samples were checked for radionuclides, metals, and water quality indicators.

The Pantex Plant Department of Energy (DOE) site was proposed for the Environmental Protection Agency's (EPA)National Priorities List (NPL) in July 1991. In August 1991, representatives of Panhandle Area Neighbors andLandowners (PANAL), Peace Farm, Serious Texans Against Nuclear Dumping (STAND), and the Texas NuclearWaste Task Force petitioned the Agency for Toxic Substances and Disease Registry (ATSDR) to conduct a publichealth assessment of the Pantex Plant; however, because of the proposed listing, ATSDR was already mandated toconduct a public health assessment of the site. The site was subsequently officially added to the NPL in May 1994.

Pantex Plant is located in the panhandle of Texas in Carson County, approximately 17 miles northeast of downtownAmarillo and 9 miles west of the town of Panhandle. The Pantex Plant boundaries are U.S. 60 to the south, TexasFarm-to-Market (FM) Road 293 to the north, FM 683 to the west, and FM 2373 to the east.(1) Figure 1 shows thelocation of the Pantex Plant.

The Pantex Plant site is primarily flat and is situated on the Southern High Plains at an elevation of approximately3,540 feet. The site is characterized as mixed prairie of native and introduced grasses. Rainwater and snow melt feednatural playas. Playa 1 also receives effluent from the primary sewage treatment lagoon. The areas adjacent to PantexPlant are primarily agricultural with typical farm residences.(2)

The Pantex Plant is owned by the U.S. Department of Energy and operated under contract by Mason and HangarCorporation. The plant is on a 16,000 acre (10,000 acres DOE owned with 6,000 acres leased as a security bufferfrom Texas Technological University) portion of the former Pantex Army Ordnance Plant. The Pantex ArmyOrdnance Plant was constructed in the first half of the 1940s by the U.S. Army for the production of conventionalordnance. The plant was deactivated at the end of World War II, and the property eventually reverted to the WarAssets Administration. In 1949, the entire installation was sold to Texas Technological College for one dollar. Theland was to be used for experimental farming but was subject to recall under the National Security Clause. TheAtomic Energy Commission (AEC) chose the site for expansion of its nuclear weapons assembly facilities in 1951. The Army Ordnance Corps reclaimed 10,000 acres of the site for the AEC and contracted the Silas Mason Companyto rehabilitate it.(1)

According to DOE, the Pantex Plant Mission is to anticipate and satisfy U.S. Department of Energy requirements byproviding competitive, quality, on-time products and services that exceed expectations and are achieved in a mannerthat protects the environment, ensures the safety and health of employees and the public, and protects our nationalsecurity. Pantex Plant's primary mission is to: assemble nuclear weapons for the nation's stockpile, disassemblenuclear weapons being retired from the stockpile, evaluate, repair, and retrofit nuclear weapons in the stockpile,demilitarize and sanitize components from dismantled nuclear weapons, provide interim storage for plutonium pitsfrom dismantled nuclear weapons, and develop, fabricate and test chemical explosives and explosive components fornuclear weapons, and support DOE initiatives.

The chemical explosives and explosive components are shipped to the Pantex Plant and fabricated into the requiredshapes for use in nuclear weapons. Other manufacturers supply all other nuclear weapons components. The PantexPlant assembles the components to produce nuclear weapons for the Department of Defense.

Maintenance and modification of weapons in the military stockpile involve partial disassembly to permit replacement,modification, or inspection of components. A statistically selected number of nuclear weapons from the militarystockpile or from initial production of a new weapons system receives a series of inspections and componentevaluations.

When a weapon is completely disassembled for retirement, the Pantex Plant separates the chemical explosives andexplosive components from the nuclear components. The recovered material is, where appropriate, offered for sale toexternal vendors for their use. A small fraction of the recovered explosives is thermally treated. The plutonium pitsare stored in the magazines in Zone 4. The plant returns all other components to their manufacturers or sends themelsewhere for reuse, salvage, or ultimate disposal. The Pantex Plant also conducts research and development work onconventional high explosives to support weapons design and development programs for the Department of Energy.

The plant is divided into several major working areas. The manufacturing area fabricates high-explosive componentsand weapon assembly/disassembly operations. The high-explosives development area supports various DOE nuclearweapons design agencies. The temporary holding area is a safe, secure place for high explosives and nuclear weaponson which no active work is under way. Other important facilities include test-firing sites for testing high explosives, alandfill disposal area, a burning ground for treatment of explosives, a water treatment plant, a steam generation plant,and a sewage treatment plant.

Pantex Plant includes short-grass prairie, a buffer zone used for agriculture, and four playas on the 4,119 hectares(10,177 acres) of DOE-owned land including Pantex Lake, and two playas on the 2,370 hectares (5,800 acres) of landleased from Texas Tech University. The DOE-owned land includes approximately 1,216 hectares (3,004 acres)dedicated to industrial operations (e.g., buildings, roads, parking areas, and mowed grass areas: 1,747 hectares (4,317acres) under cultivation; and 720 hectares (1,779 acres) used for domestic livestock grazing). The 436 hectares (1,077acres) at Pantex Lake are used for domestic livestock grazing and farming.(2)

Representatives of the Agency for Toxic Substances and Disease Registry (ATSDR) first visited the Pantex facilityDecember 2-5, 1991, as part of a program to evaluate Department of Energy (DOE) National Priorities List (NPL)sites and develop a sequential workplan to address those sites. Agency staff members used the site-ranking schemepublished in the Federal Register (57 FR 37382) to rank each of the DOE sites. Rankings established the basis fora relative order for the efficient application of limited personnel and budget resources. The Pantex Plant's ranking,compared with rankings of other national DOE sites, qualified it for initiation of a public health assessment in 1995. ATSDR conducted a subsequent site visit September 11-14, 1995, to obtain information for conducting the scheduledpublic health assessment of the Pantex Plant. During that visit, ATSDR staff members met with representatives of theTexas Natural Resources Conservation Commission (TNRCC) and the Pantex Plant Citizens' Advisory Board(PPCAB) Planning and Training Subcommittee. ATSDR staff members also attended on-site briefings by PantexEnvironmental staff members, toured the site, and reviewed historical documents pertaining to environmentalsampling and remediation activities.

ATSDR staff briefed the full membership of the PPCAB on September 26, 1995 on ATSDR's mission and how thePantex Public Health Assessment would be conducted. ATSDR staff provided subsequent presentations to thePPCAB on February 27, March 26, April 30, August 27, September 24, November 26, 1996 and July 22, 1997 on theprogress of the health assessment.

ATSDR held public meetings the first week in March 1998 to present the Pantex Plant Public Health Assessment andgather public comments on the health assessment. Meetings were held at the War Memorial Building in Panhandle,Texas (March 2nd and 3rd); Vickie's Grill on Highway 136 in Amarillo, Texas (March 3rd); the Amarillo CentralLibrary (March 4th); and the Amarillo Association of Realtors Building (March 5th). Approximately 21 communitymembers attended the public meetings.

Summary Population Statistics Methodology: The potentially impacted site area was spatially defined as the area within the site boundary plus a one-mile buffer around that boundary. A one-mile bufferis useful for conveying information about the demographic structure of the area adjacent to the site and identifies thosewho might have a greater potential for exposure. It is important to note, however, that proximity, in itself, is not anadequate indicator of exposure to site-related contaminants. Proximity measures must be supplemented withenvironmental pathway information to evaluate exposed populations.

The Agency for Toxic Substances and Disease Registry (ATSDR) used an "area proportion" technique to calculate thesummary population statistics presented. When combining census blocks with buffer distances, the periphery of theobtained boundary commonly intersects a census block. In such cases, applying an area weight factor to thepopulation variables of interest is arguably the best choice for collecting site-specific demographic population data. The population in a census block is weighted to reflect the proportion of the block area that is actually in the bufferedsite area. This method assumes that the population is uniformly distributed throughout the block.

ATSDR demographic data sources are:

U.S. Bureau of the Census. 1990. Public Law 94-171 [machine-readable data files]. The Bureau,Washington, D.C.

U.S. Bureau of the Census. 1991. Census of Population and Housing, Summary Tape File 1 [machine-readable data files]. The Bureau, Washington, D.C.

Regional Demography: The 1990 census of the residential population surrounding Pantex Plant showed that most ofthe population is located west-southwest of the Pantex Plant in the Amarillo metropolitan area. Figures 2 through 11show the population density and distribution for the following demographic variables: one mile site buffer, from 10 to25 miles from the site boundary, and for susceptible populations such as children 6 years and younger, females aged15 to 44, and adults 65 and older. The cumulative population within a 1, 5, 10, and 25 mile radius of the Pantex Plantwas 36, 413, 6138, and 200857 respectively.

As of the 1990 Census, Amarillo had 157,615 residents. Pampa, Texas, located about 40 miles east-northeast of thePantex Plant, is the second largest population concentration, with about 21,000 residents. The remaining populationwithin the 25 mile radius is fairly evenly distributed at a density of about three people per square mile.(3)

The cultural and ethnic origins in the region are diverse, although historical trends are still reflected in the overallpopulation composition. The population is predominantly white, with origins back to early settlers who relocatedfrom the eastern U.S. and who were primarily European. Persons of Hispanic origin comprise the second largest group in the area.(4)

Land Use: The area around Pantex Plant is semiarid. Land is used mainly for farming and ranching. Althoughdryland farming is dominant, some fields are irrigated from the Ogallala aquifer or, less commonly, from local playas. Ranching in the region is primarily cow-calf operations. Several significant industrial facilities are located in thegeneral area, including two electric power plants, a copper refinery, a beef packing plant, and the Amarillo International Airport with associated industries.(3)

Regional Hydrogeology: The land surface in the vicinity of the Pantex Plant is relatively flat and is dominated byshallow ephemeral lakes called playas. All surface drainage flows into these playas, of which 4 are located within theDOE-owned Pantex Plant boundaries. Rainfall averages between 18 and 20 inches/year; however, surface evaporationis up to five times greater than precipitation. Surficial deposits in the Pantex area are composed of Quaternary andRecent Eolian deposits (well sorted, fine grained sands and clays) that contain concentrations of clay and carbonate.

Two aquifers, the Dockum Group aquifer and the Ogallala aquifer, are present in the region. The Dockum Groupaquifer occurs at depths varying between 350 and 700 feet below ground surface in the region. Little recharge of theDockum Group aquifer occurs in the Pantex area (less than 1 inch per year), and the potentiometric surface has notbeen established in this area. The direction of flow may be towards the southwest, but the hydraulic gradients havenot been determined. In most of the region, the Dockum Group aquifer is thought to be semi-confined andhydraulically separated from the overlying Ogallala aquifer. In the Pantex vicinity, however, the confining units aremissing, and the two aquifers are thought to be hydraulically connected.

The Ogallala aquifer occurs in permeable sediments comprising the basal portion of the Ogallala Formation, whichhave an average potential hydraulic conductivity of 22.5 feet/day. The Ogallala aquifer is unconfined in this regionand occurs at depths between 280 and 460 feet with overall thicknesses of 50 to more than 350 feet in the Pantexvicinity. The regional gradient of the Ogallala is to the southeast and is locally different in the vicinity of Pantex Plantin that the gradient is east to northeast. Pumping at the City of Amarillo wellfield (just north of the Pantex Plant) hascaused the shift in groundwater flow. Pumpage exceeds recharge by a factor of 24 and the net result is that pumpingof the Ogallala aquifer has lowered the static level of the aquifer by about 2 feet/year. Recharge to the Ogallalaaquifer occurs at a rate of less than 1 inch per year from vertical leakage in high permeability areas and preferentialpathways from the playa basins. The central portions of the playas are underlain by relatively thick, impermeableclays. During infrequent, heavy rainfalls, playa water levels exceed the central areas and move downward andrecharge the underlying aquifer. Where impermeable units, predominantly clay, are present at depth, downward flowis restricted and areas of perched water are present. On-site at the Pantex Plant, perched groundwater with saturatedthicknesses of 0 - 75 feet at depths between 210 and 300 feet BGL (below ground level, as opposed to below MSL--mean sea level--a different reference data point) has been identified through the installation of 67 perched aquiferwells. The direction of flow for the perched groundwater is radially outwards from Playa 1 and Zone 12 with themajor flow component to the southeast.(5)

Agency for Toxic Substances and Disease Registry (ATSDR) and Texas Department of Health (TDH) staff evaluatedcommunity health concerns as part of the public health assessment process. Staff identified the following communityhealth concerns during meetings with concerned residents in April, June, and August, 1996:

potential for airborne exposure as a result of open burning and dispersal of explosive residues andsediments from dry surface impoundments;

asbestos disposal area in the northeastern corner of the plant; and

public health impact of previous discharge of waste waters from Pantex and the old Air Force base to Pantex Lake, an off-site naturally occurring playa northeast of the plant.

For many of the health concerns, residents requested information for the eight counties closest to the Pantex Plant. After further discussion, TDH concluded that information on a four-county area would be sufficient to addressresidents concerns. This choice would be consistent with areas considered in previous cancer cluster investigations.